Messages in this thread | | | Date | Fri, 10 Oct 2008 11:01:17 +0200 | From | Jens Axboe <> | Subject | Re: [PATCH 4/7] ide: ide_hwgroup_t.rq doesn't need an ide_lock held |
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On Fri, Oct 10 2008, Elias Oltmanns wrote: > Bartlomiej Zolnierkiewicz <bzolnier@gmail.com> wrote: > > From: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com> > > Subject: [PATCH] ide: ide_hwgroup_t.rq doesn't need an ide_lock held > > > > While at it: > > - no need to check for hwgroup presence in ide_dump_opcode() > > > > Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com> > > --- > [...] > > Index: b/drivers/ide/ide-io.c > > =================================================================== > > --- a/drivers/ide/ide-io.c > > +++ b/drivers/ide/ide-io.c > [...] > > @@ -274,7 +269,11 @@ static void ide_complete_pm_request (ide > > drive->dev_flags &= ~IDE_DFLAG_BLOCKED; > > blk_start_queue(drive->queue); > > } > > - HWGROUP(drive)->rq = NULL; > > + spin_unlock_irqrestore(&ide_lock, flags); > > + > > + drive->hwif->hwgroup->rq = NULL; > > + > > + spin_lock_irqsave(&ide_lock, flags); > > if (__blk_end_request(rq, 0, 0)) > > BUG(); > > spin_unlock_irqrestore(&ide_lock, flags); > > Is it really an improvement to release the lock here?
And more importantly, is it even safe? What serializes ->rq assignments and checks without the ide_lock? Looks fishy.
But yes, dropping a lock for an assigment just to regrab it right after is never a win. There's no contention gain, but possible bouncing problems.
-- Jens Axboe
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